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Food chemistry 2 > Enzymes > Flashcards

Enzymes Flashcards

1
Q

salting out

A

when salt concentration becomes such that molecules become less soluble and will precipitate bc salt is more interested in interacting with itself

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2
Q

salting in

A

adding salt so that the molecules become more soluble, will reach a finite max point and then decrease and move into salting out

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3
Q

precipitation with organic solvents does what to proteins solubility?

A

reduces protein solubility because it reduces surface hydration ( the thin rim of moisture around a protein) and increases the hydrophobic surface which promotes aggregation just as salting out does

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4
Q

what is the principle effect of precipitation with organic solvents?

A

reduction of water activity

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5
Q

how do you ensure that the enzyme does not become deactivated when using solvent precipitation?

A

low temp

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6
Q

cations exchangers bind to ?

A

cations and then anions are eluted

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7
Q

anion exchangers bind to ?

A

anions, so cations are eluted

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8
Q

strong ion exchangers

A

shows no change in ion exchange capacity with changes in pH

stay stable’s in large pH range

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9
Q

weak ion exchangers

A

get ionized over a limited pH range. restrictive in the pH range, do not retain there charges well

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10
Q

example of weak ion exchanger?

A

carboxymethyl cellulose

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11
Q

example of a strong ion exchanger?

A

sulphuric acid

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12
Q

isoelectric focusing

A

the molecules migrate and then stop at the pH corresponding to the pI

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13
Q

methods to test that an enzyme is pure?

A
  • homogeneity- one band in electrophoresis
  • chromatographic behavior
  • activity testing
  • isoelectric testing
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14
Q

expand on chromatographic behaviour in testing for enzyme purity?

A

plot a graph with ABS on Y and fraction number on X

-

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15
Q

glucose oxidase can oxidize glucose into

A

less sweet gluconic acid

sometimes referred to as desugaring agent

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16
Q

what reaction is used to remove O2 from reaction mixture?

A

glucose oxidase

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17
Q

transglutaminase is used for

A

forming isopeptide bond bc formed between the side chains and makes molecule bigger- food texture in imitation fish

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18
Q

lyases

A

act on double bonds, to break or create

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19
Q

ligases

A

smaller to bigger molecules

glue together

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20
Q

how is catalysis measured?

A

either through product formation or substrate dissaperence

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21
Q

initial rate method

A

take measurement as close to zero as possible
- at the start you expect the enzyme to be the most active (most potent), the substrate concentration is at max and there should be no product formed

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22
Q

end point method

A

take measurement after leaving reaction to proceed for an interval of time
- sub concentration is depleted, products would affect negative feedback inhibition
enzyme could lose activity over time

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23
Q

which requires more skill and expensive equipment?

A

initial rate method

24
Q

what is happening in steady state (region b)

A

break down and forming at the same time

25
Q

irreversible inhibitors examples

A

PMSF

DIFP- a nerve poison

26
Q

difference in binding between irreversible and reversible inhibitor?

A

irreversible inhibitors bind covalently

reversible bind non-covalently

27
Q

wine making and brewing use? (2)

A

proteases and amylases

28
Q

Carbs turn to _______ ( by amylases and carbohydrases

A

simple sugars

29
Q

simple sugars turn to _______- (by yeasts)

A

alcohol

30
Q

what is the purpose of using proteases in wine making?

A

they break down proteins into soluble peptides that remain in the solution even during cold storage

31
Q

what is chill proofing of beer/wine? how is it achieved?

A

treatment to prevent the development of haziness or cloudiness due to precipitation of proteins when beer is chilled. Treatments include the addition of tannins to precipitate proteins, materials such as bentonite to adsorb them and proteolytic enzymes to hydrolyse them.

32
Q

describe proteases role in baking?

A

break down gluten –> make dough more pliable

33
Q

why add lipoxygenases to baking?

A

break down carotenoid pigments to cause the whitening or bleaching of flour

34
Q

why add amylases to baking?

A

converts starch to dextrins, oligosaccharides, and the sugar maltose. Maltose provides a fermentable sugar for the yeast–> CO2 production–> loaf volume

35
Q

Transglutaminases (TGase) is used in meat too?

A

improve texture by bringing smaller molecules together

  • strong cross-linking
  • uses in gelatine, fish, meat, whey, bakery etc
  • tenderize/ restructure meat
  • brings aa’s together
36
Q

endoproteases

A 
used to achieve more extensive changes in the structure of a protein
split peptide chain in the middle
-pepsin
-trypsin
-chymotrypsin
-elastase
37
Q

exoproteases

A

split peptide chain at the end -remove aa residues from the terminals of proteins

  • used to debater peptides and proteins
  • carboxypeptidases
  • aminopeptidases
38
Q

cellulose is linked by?

A

beta 1-4 links
- Cellulose is a linear polysaccharide polymer with many glucose monosaccharide units. The acetal linkage is beta which makes it different from starch.

39
Q

starch is linked by?

A

amylose which is alpha 1,4 and amylopectin which is alpha 1,6 links

40
Q

starch or cellulose more compact?

A

cellulose
- straight molecule
and more resistent to enzyme hydrolyses

41
Q

don’t want oxygen in a reaction, use?

A

glucose oxidase

42
Q

4 benefits of using food enzymes?

A

natural
specificity
activity under mild conditions
ease of control

43
Q

cheese making

A

rennin which contains proteolytic enzymes (chymosin and pepsins) turns caseinogen into insoluble casein- curdling milk

44
Q

describe milk proteins and rennins role in curdling milk

A

In essence, kappa casein normally keeps the majority of milk protein soluble and prevents it from spontaneously coagulating- bc negative tails keep them repelling each other
- Chymosin proteolytically cuts and inactivates kappa casein, converting it into para-kappa-casein and a smaller protein called glycomacropeptide. Para-kappa-casein does not have the ability to stabilize the micellar structure and the calcium-insoluble caseins com together and precipitate, forming a curd.

45
Q

describe alchohol fermentation biochemically?

A

after glycolysis= pyruvate

  • alcoholic fermentation, this is a two-step process
  • first involves the Enzyme pyruvate decarboxylase (PDC). The pyruvate is decarboxylated to an acetaldehyde. This acetaldehyde then undergoes a reaction catalyzed by alcohol dehydrogenase to produce ethanol; this is the step in which the NAD+ is restored
46
Q

in food processing what is of most interest in lipid reactions?

A

hydrolysis of acyl glycerides

  • mostly unfavourable
  • undesired odors

TG + H2O–> glycerol and FFA

47
Q

when is the action of lipase desirable?

A

low molecular weight products- flavour

buttermilk, baked goods, roquefort cheese

48
Q

important oxidoreductase reaction in food processing?

A 
ascorbic acid oxidase
polyphenol oxidase
glucose oxidase
catalase
lipoxygenase
xanthine oxidase
peroxidase
49
Q

ascorbic acid oxidase

A

It can be oxidized by losing two protons and two electrons, but normally loses only one electron at a time

50
Q

industrial application of proteases

A 
remove bitterness
modify milk and whey
hydrolysis of heat gluten
alcohol beverages
baking
recovery of scrap
51
Q

lesser known applications of enzymes

A

-remove dental plaque
-elimination of hair with —keratinase
solubilization of cold tea solids with tannates

52
Q

tannases

A

solubilization of cold tea solids

53
Q

keratinase

A

elimination of hair

54
Q

dextranases

A

remove dental plaque

55
Q

controlling enzymes

A

temp, pressure, Aw, chemicals, enzyme (killer enzyme/anti-enzyme enzymes)

56
Q

whey proteins can be hydrolyzed to _______, which are less alergetic

A

hydrolysates

57
Q

removal of plaque

compounds in toothpastes

A

lysozyme break cell walls of bacteria
dextrine’s break dow sugars
proteases

Food chemistry 2 (7 decks)

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